The present invention is directed to automotive power transmission devices, and in particular to an electromechanically actuated clutch useful for automotive couplings, differentials and transmissions.
Automotive power transfer systems face many demands from consumers. Users of automobiles, trucks, and even off-road vehicles expect their vehicles to get them safely and quickly to their destination, no matter what the obstacles or road conditions. Automotive differentials allow two wheels mounted on output half shafts to rotate at different speeds, helping trucks and cars accomplish turns. However, in a conventional differential, when one wheel loses traction, the other wheel may also lose power. In a limited slip differential, when one wheel has less traction with the road than the other wheel, power is transferred from the slipping wheel to the non-slipping wheel. Under these conditions, the wheel that slips has an opportunity to regain traction, while the wheel that grips has increased power to keep moving and perhaps to keep the vehicle moving.
Some positive limited slip differentials are presently in the marketplace. One problem with such differentials, such as those depicted in U.S. Pat. No. 6,261,202, is that they tend to be controlled by the relative speed of the wheels as well as a force or a preload applied to side gears in the differential. Another problem is that the driver or operator has little control over when the differential engages and begins to transfer power. It would be useful if there were a slipping differential that could be controlled automatically, or that would automatically engage when needed. It would also be helpful if the differential could engage a drive shaft with a mechanism less complicated than the present implementation, such as the type of device depicted in U.S. Pat. No. 5,938,556. The differential depicted in this patent is very complicated and uses numerous friction clutch plates and a great many parts requiring tight manufacturing tolerances.
What is needed is a clutch assembly requiring less complicated parts and assembly, and yet having a reliable ability to engage and disengage a driving member from a driven member. What is also needed is a differential that can be engaged or disengaged upon demand by a vehicle and driving conditions experienced by the vehicle.
One aspect of the invention is a cone friction clutch for engaging a shaft. The clutch comprises a carrier having a tapered bore and an external gear defined thereon. The external gear is meant for engaging a source of mechanical power, such as a ring gear. The clutch includes a tapered piston within the bore and means for moving the tapered piston into contact with the carrier. The tapered piston may rotate with the shaft. The clutch also includes means for controlling the movement of the piston. The means for controlling causes the means for moving to move the tapered piston into contact with the carrier. Power is thus transmitted between the carrier and the shaft.
Another aspect of the invention is a clutch for engaging a shaft. The clutch comprises a carrier having a first tapered bore and an external gear. A first tapered piston is provided within the bore, the piston surrounding and rotating with the shaft. There is a first mechanism for moving the tapered piston, the mechanism selected from the group consisting of a ball and ramp mechanism, a hydraulic pump, and a solenoid. There is also a controller for controlling a movement of the mechanism and the piston into contact with the carrier. Thus, power is transmitted between the carrier and the shaft.
Another aspect of the invention is a coupling for use in a power transmission having an on-demand shaft. The coupling comprises a carrier having a tapered bore and an external gear defined thereon, and also comprises a tapered piston with the bore for rotating with the shaft. A mechanism for moving the tapered piston is provided and is selected from the group consisting of a ball and ramp mechanism, a hydraulic pump, and a solenoid. There is also a controller for controlling movement of the tapered piston. The controller controls movement of the mechanism and the piston into contact with the carrier, and power is then transmitted between the carrier and the shaft.
Another aspect of the invention is a method for engaging a shaft. The method comprises providing a cone-friction clutch with a tapered piston for engaging the shaft. The method then includes controlling movement of the piston through an electronic controller, and moving the piston into engagement with the shaft. Many embodiments and other aspects of the invention will be readily apparent in view of the drawings and detailed descriptions provided below.